1. Field of the Invention
The present invention relates generally to a display apparatus and an electronic camera, and more particularly to an LCD apparatus, which is applied to an electronic camera such as a digital camera, and an electronic camera.
2. Description of Related Art
Conventionally, to display a still image captured by a digital camera, etc. on a liquid crystal display (LCD), image data of the still image is stored in an image memory, the image data is then read from the image memory and converted into a standard video signal (e.g., NTSC or PAL) or a video signal suitable for the LCD. The video signal is applied to the LCD so that the still image can be displayed on the LCD.
During the display, the image memory is continuously accessed at a constant frame rate through a memory bus. Thus, in order to retrieve the image data from the image memory for another purpose of compressing the image data or recording the image data in an external storage medium, etc., it is necessary to stop the display temporarily or to retrieve the image data during only vertical and horizontal blanking periods.
If the display is temporarily stopped, it is impossible to confirm the image during that time. If the image data is retrieved during the vertical and horizontal blanking periods, it takes a long time to process the data as a whole, since the vertical and horizontal blanking periods are very short. For example, when an image of 640xc3x97480 pixels is displayed by means of the NTSC video signal,
xe2x80x9cOne-frame periodxe2x80x9d ={fraction (1/30)}=33.3 msec, and xe2x80x9cVertical blanking periodxe2x80x9d =xe2x80x9cOne-frame periodxe2x80x9d xc3x97(525xe2x88x92480)/525=({fraction (1/30)})xc3x97{fraction (45/525)}∞2.86 msec.
That is, if only the vertical blanking periods are used, the data is processed for only 2.86msec in each vertical synchronous period. Even if the horizontal blanking periods are also used, the processing time increases only a little.
There is proposed an electronic camera with an LCD monitor, which can also serve as an electronic finder for enabling a user to determine what will be included in the picture by displaying moving images captured through an imaging unit of the camera. This electronic camera, however, has a problem of consuming a large amount of electricity during the use of the LCD monitor.
It is an object of the present invention to provide a display apparatus and an electronic camera that reduce the consumption of electricity while an image is displayed on a display unit.
It is another object of the present invention to provide an electronic camera, which is capable of performing a signal processing at a high speed while displaying an image on the display unit.
To achieve the above-mentioned object, the present invention is directed to a display apparatus comprising: a display unit; a video signal generator for intermittently outputting a video signal; and a display unit driver for intermittently receiving the video signal from the video signal generator and applying the video signal and drive pulses to the display unit; wherein, while the display unit driver does not receive the video signal from the video signal generator, the display unit driver suspends applying of at least a part of the drive pulses to the display unit and maintains a currently-displayed image on the display unit.
To achieve the above-mentioned object, the present invention is also directed to an electronic camera comprising: an imaging device for converting light from a subject into an image signal; an imaging unit for obtaining image data representing the subject by driving the imaging device; a display unit; a video signal generator for controlling the imaging unit to intermittently drive the imaging device, intermittently converting the image data obtained through the imaging device and the imaging unit into a video signal, and intermittently outputting the video signal; and a display unit driver for intermittently receiving the video signal from the video signal generator and applying the video signal and drive pulses to the display unit; wherein, while the display unit driver does not receive the video signal from the video signal generator, the display unit driver suspends applying of at least a part of the drive pulses to the display unit and maintains a currently-displayed image on the display unit.
To achieve the above-mentioned object, the present invention is directed to an electronic camera comprising: an imaging device for converting light from a subject into an image signal; an imaging unit for obtaining image data representing the subject by driving the imaging device; an image memory for storing the image data; a display unit; a video signal generator for intermittently reading the image data from the image memory, intermittently converting the image data read from the image memory into a video signal, and intermittently outputting the video signal; and a display unit driver for intermittently receiving the video signal from the video signal generator and applying the video signal and drive pulses to the display unit; wherein, while the display unit driver does not receive the video signal from the video signal generator, the display unit driver suspends applying of at least a part of the drive pulses to the display unit and maintains a currently-displayed image on the display unit.
The display unit may comprise an LCD.
The present invention has been developed in view of the fact that some kinds of display units including the LCD can continue displaying the image for a constant period by applying voltage corresponding to the image data to each element between the terminals thereof, even if the application of the video signal and the drive pulses is suspended. According to the present invention, the video signal is intermittently applied to the display unit. While no video signal is applied, the drive pulse for the display unit is not generated, and the display unit continues displaying the currently-displayed image. It is therefore possible to stop driving the imaging device and stop reading the image data from the image memory while no video signal is applied. This significantly reduces the consumption of electricity. Stopping driving the display unit has no problem if the display unit displays a still image. If the display unit displays a moving image, the moving image is displayed intermittently and cannot be displayed smoothly, but the display unit LCD can satisfactorily serve as the electronic finder.
To achieve the above-mentioned object, the present invention is directed to an electronic camera comprising: an imaging device for converting light from a subject into an image signal; an imaging unit for obtaining image data representing the subject by driving the imaging device; an image memory for storing the image data; a display unit; a video signal generator for intermittently reading the image data from the image memory, intermittently converting the image data read from the image memory into a video signal, and intermittently outputting the video signal, the video signal generator being capable of continuously reading the image data from the image memory, continuously converting the image data read from the image memory into the video signal, and continuously outputting the video signal; a signal processor for accessing the image memory to perform a signal processing while the video signal generator does not read the image data from the image memory; and a display unit driver for intermittently receiving the video signal from the video signal generator and applying the video signal and drive pulses to the display unit; wherein, while the display unit driver does not receive the video signal from the video signal generator, the display unit driver suspends applying of at least a part of the drive pulses to the display unit and maintains a currently-displayed image on the display unit.
According to the present invention, in the case of performing a signal processing (e.g., compressing the image data and recording the image data in the external storage medium) during the image data is read from the image memory for the display on the display unit, the image data is intermittently read from the image memory and the display unit is intermittently driven. Thus, the image data is not always read from the image memory for the display on the display unit. For this reason, it is possible to secure enough time to perform other signal processing using the image data in the image memory and perform the signal processing at a high speed.
Preferably, the electronic camera further comprises: a video output terminal for operatively connecting to an external device, the video signal outputted from the video signal generator being outputted to the external device through the video output terminal; and a detector for detecting the video output terminal operatively connecting the external device; wherein, when the detector detects the video output terminal operatively connecting the external device, the video signal generator continuously reads the image data from the image memory, continuously converts the image data read from the image memory into the video signal, and continuously outputs the video signal.
According to the present invention, if the video output terminal connects to the external device such as a television, the video signal is outputted continuously, not intermittently, since it is necessary to output the standard (not intermittent) video signal of NTSC or PAL etc. to the external device through the video output terminal.
Preferably, in the electronic camera, the signal processor performs the signal processing including recording the image data stored in the image memory into a storage medium; and the video signal generator intermittently reads the image data from the image memory since a release of the electronic camera is operated until the image data is recorded in the storage medium.
To achieve the above-mentioned object, the present invention is directed to an electronic camera comprising: imaging device for converting light from an object into an image signal; imaging means for acquiring image data representing the object by driving the imaging device; a liquid crystal display (LCD); a video output terminal for outputting video signals to outside; selection means for selecting whether to output the video signals through the video output terminal or to display an image on the LCD; timing signal generating means for generating a first timing signal suitable for generating standard video signals if the selection means selects outputting the video signals and generating means generating a second timing signal with a lower frequency than the first timing signal if the selection means selects displaying the image on the LCD; video signal generator for controlling the imaging means to drive the imaging device with the first timing signal if the selection means selects outputting the video signals, converting the image data acquired through the imaging device and the imaging means into the standard video signals, and outputting the standard video signals; and LCD driving means for driving the imaging means to drive the imaging device with the second timing signal if the selection means selects displaying the image on the LCD, converting the image data acquired through the imaging device and the imaging means into video signals suitable for display on the LCD, and outputting the video signals and drive pulses corresponding to the video signals to the LCD.
To achieve the above-mentioned object, the present invention is also directed to an electronic camera comprising: an imaging device for converting light from a subject into an image signal; an imaging unit for obtaining image data representing the subject by driving the imaging device; a display unit; a video output terminal for operatively connecting to an external device; a selector for selecting one of a first mode to output a first video signal to the external device through the video output terminal and a second mode to display an image represented with the image data on the display unit; a timing signal generator for generating, in the first mode, a first timing signal to generate the first video signal, and generating, in the second mode, a second timing signal with a lower frequency than the first timing signal; a video signal generator for, in the first mode, controlling the imaging unit to drive the imaging device with the first timing signal, converting the image data obtained through the imaging device and the imaging unit into the first video signal, and outputting the first video signal; and a display unit driver for, in the second mode, controlling the imaging unit to drive the imaging device with the second timing signal, converting the image data obtained through the imaging device and the imaging unit into a second video signal, and applying the second video signal and drive pulses to the display unit.
To achieve the above-mentioned object, the present invention is also directed to an electronic camera comprising: an imaging device for converting light from a subject into an image signal; an imaging unit for obtaining image data representing the subject by driving the imaging device; an image memory for storing the image data; a display unit; a video output terminal for operatively connecting to an external device; a selector for selecting one of a first mode to output a first video signal to the external device through the video output terminal and a second mode to display an image represented with the image data on the display unit; a timing signal generator for generating, in the first mode, a first timing signal to generate the first video signal, and generating, in the second mode, a second timing signal with a lower frequency than the first timing signal; a video signal generator for, in the first mode, reading the image data from the image memory with the first timing signal, converting the image data read from the image memory into the first video signal, and outputting the first video signal; and a display unit driver for, in the second mode, reading the image data from the image memory with the second timing signal, converting the image data read from the image memory into a second video signal, and applying the second video signal and drive pulses to the display unit.
According to the present invention, if the video output terminal connects to the external device such as a television, the imaging device are driven or the image data is read from the image memory with the first timing signal suitable for generating the first or the standard video signal of NTSC or PAL etc., since it is necessary to output the standard video signal to the external device through the video output terminal. On the other hand, to perform the display on the display unit, it is unnecessary to confirm the format of the standard video signal. Thus, the imaging device is driven or the image data is read from the image memory with the second timing signal of the lower frequency than the first timing signal, and the second video signal for the display unit and the drive pulses corresponding to the video signal are generated. The consumption of electricity in each circuit is proportional to the frequency of the timing signal, with which the imaging device are driven and/or the image data is read from the image memory. For this reason, using the low frequency timing signal for the display on the display unit reduces the consumption of electricity.